The present invention relates to a process and apparatus for controlling the cloth feeder of a sewing machine.
As is known, an approximately rectangular movement is imparted to the cloth feeder of customary sewing machines during the sewing procedure, i.e. the cloth feeder is lifted from a low, ineffective position, upwardly past the needle plate, moved forward in the cloth feeding direction, then lowered below the needle plate, and finally moved back into the starting position. During this operation, the movements of the needle and of the cloth feeder are synchronized in such a way that the feeding of the sewing material takes place while the needle is in the uppermost zone of its upward movement. The cloth feeder thus projects beyond the working surface with the needle in the lifted position. Since the action of the cloth feeder is undesirable for performing certain objectives, for example for darning, embroidering, and the like, level-adjustable needle plates or cover plates have been proposed which take care of maintaining the cloth feeder, even in its lifted operating position, beneath the working plane and thus in an ineffective state. However, since the cloth feeder, when projecting above the working plane, also interferes with the correct positioning of the sewing material under the sewing site before initiating the sewing operation, or with other manipulations of the sewing material, different, manually operable devices have also become known, by means of which the cloth feeder can be lowered in each case. On the other hand, for positioning and/or manipulation of the sewing material, the presser foot must in each instance be lifted at least to such an extent (for example by hand or by knee manipulation) that it no longer exerts pressure on the sewing material. The unhindered shifting of the sewing material on the working surface thus makes it necessary in the conventional machines to operate, in addition to the device for lifting the presser foot, also the device for lifting the needle plate and/or for lowering the cloth feeder. This procedure is cumbersome and does not permit rapid working. Of course, analogous considerations apply after the lowering of the presser foot, when the cloth feeder must be returned to its operative position.
These disadvantages are avoided by the process of the present invention by providing that the cloth feeder, during the lifting of the presser foot by means of the operating element associated therewith, is simultaneously placed into its lowered position and, upon lowering of the presser foot, is again released for the lifting movement. Accordingly, a single operating step suffices for the simultaneous release of the working surface from the presser foot as well as from the cloth feeder.
The apparatus for conducting the present process, likewise forming the subject matter of the present invention, comprises a coupling mechanism between the presser foot lifting device and the lifting mechanism for the cloth feeder, which latter is acted upon along the lines of lowering the same, this coupling mechanism, upon operation of the lifting device along the lines of lifting the presser foot, simultaneously disengaging the lifting mechanism of the cloth feeder from its driving element and thus lowering the loaded (acted-upon) cloth feeder.
Due to this arrangement, the cloth feeder is, with certainty, lowered simultaneously upon lifting the presser foot by means of the lifting device and, conversely, upon the lowering of the presser foot by means of the lifting device, the coupling mechanism is again placed in readiness for coupling the lifting mechanism of the cloth feeder with its driving element.
Particularly suitable is an installation wherein the coupling mechanism, is operable by the operating element of the lifting device which is actuatable, for example, by a toggle lever and is, also by means of a separate, manual operating element not operable affecting the lifting device, for the activation and deactivation of the lifting mechanism for the cloth feeder. In such an installation the manual operating means customary in sewing machines for the direct lifting and lowering of the pressure foot does not affect the coupling mechanism.